Turning quota ON

Is giving me this error at the system boot; quotaon: using //aquota.user on /dev/sda2 [/] Invalid Argument.
I look on the boot.msg file and found that /dev/sda2 not shows in the mounting file system section.
But when I manually try to mount tells me this device is already mounted. But in the case of /dev/sda3 the quota is turned on perfectly. Any clues